(1) Field of the Invention
The invention relates to a light shielding structure adopted for use on reflected mirrors, and more particularly to a light shielding structure for a light-guide module of an image scanning apparatus or a multi-functional peripheral to prevent redundant light reflection of reflected mirrors of the light-guide module or noise signals from projecting to an image sensing device.
(2) Description of the Prior Art
Under the present demand for improving image resolution and shrinking device size, there is a constant requirement for image process apparatus (such as scanners or MFPs) to adopt an advanced design in the optical processing mechanism that generates digital image signals.
Refer to FIG. 1 for a conventional scanning device 10. It includes a cover plate 101, a light source 102, a scanning deck 104, a light-guide module 106, a lens 108 and an image sensing device 110. The cover plate 101 aims to cover a scanning object 30 located on the scanning deck 104. The light source 102 emits light to the scanning object 30. The light is reflected by the scanning object 30 and passes through an entrance 1066 to the light-guide module 106. The light-guide module 106 has a reflected mirror set which includes reflected mirrors. Four reflected mirrors 1061, 1062, 1063 and 1064 are taken as an example shown in FIG. 1. The reflected mirrors 1061 through 1064 aim to transmit light according to a preset light route to the lens 108. The lens 108 converges the light to become an image on the image sensing device 110 which transforms the receiving image light to digital signals. The light-guide module shown in FIG. 1 may be used on scanning apparatus and other image process devices such as MFPs.
With proper calibration, an incident light can project accurately to the center area of the four reflected mirrors shown in FIG. 1 and be precisely directed to the image sensing device. But the conventional reflected mirrors often are too big and light from other non-relevant light sources often occurs and projects to the light sensing device 110, such as an external light 1023 shown in FIG. 1. As a result, the scan image generated by the conventional scanning device 10 often is blurred by black shadows or noise signals.
Moreover, the light reflected by the object 30 also has incident angle problem, such as the light reflected by the first reflected mirror 1061 might directly project to the fourth reflected mirror 1064 and be directed to the image sensing device 110 (indicated by lights 1021 and 1022 shown in FIG. 1). Or some lights are directly projected to the fourth reflected mirror 1064 and form erratic reflection to the image sensing device 110 (many other erratic light reflections might also occur. They are not indicated in FIG. 1 to smooth reading). All this erratic reflection will generate redundant scanning images on the conventional scanning device 10 and result in undesirable scanning quality. This becomes even more serious in the high resolution.
In addition, in the event of the calibration of the reflected mirrors is not properly done such as the one shown in FIG. 1 (not accurate positioning of the reflected mirrors), even if the light is projected to the center area of the reflected mirror, the reflected light could deviate and cannot travel on the correct light route and project correctly to the reflected mirrors at the later stages. While the light might finally be reflected to the light sensing device, it is not a normal reflection and redundant scan images occur.
Therefore to design the reflected mirrors at a correct size to reflect light accurately without an extra reflecting area to reflect erratic light or noise signals is a goal pursued by scanner or MFP makers. However, due to fabrication technique and material constraints, there is a limitation for the dimension of the reflected mirrors. It is very difficult to produce reflected mirrors that fully meet the requirements. As the prevailing trend of product design demands compact size, to shrink the size of the reflected mirrors often result in mirror shattering and higher cost. Production and assembly become more complicated. Any damage of the reflected mirrors will increase the fabrication cost and time. When the reflected mirrors are too small, calibration of the reflected mirrors to form a correct light route also is more difficult. This is another concern of the design.
In view of the foregoing disadvantages, there is a need to provide a novel design for the reflected mirrors to overcome the problems of erratic reflection and noise signals occurred to the excessive size of the reflected mirrors, and the shattering and high cost occurred to the small size of the reflected mirrors.